1. Field of the Invention
The present invention relates to the application of a viscous material on a sealing surface, and more particularly is directed to improvements in the application of frit slurry to a sealing surface of a funnel-shaped member of a cathode ray tube.
2. Description of the Prior Art
In assembling various types of glass display tubes such as, for example, in securing a glass face plate member of a cathode ray tube to a glass funnel-shaped rear member thereof, a stripe of frit slurry is applied, for example, to an edge or sealing surface of the funnel-shaped rear member, and the face plate member is thereafter placed against the coated sealing surface of the funnel-shaped rear member. The two members are then heated to a temperature which causes the frit slurry to fuse and thereby unite the members.
According to the prior art, an apparatus used for supplying frit slurry during assembly of the cathode ray tube includes a pump through which the slurry travels and which provides the necessary driving force required to transport the frit slurry from a holding tank to the sealing surface to be coated. However, if the viscosity of the slurry is increased, which may be desirable for various reasons, the pump becomes clogged with dried slurry, and this is especially the case with viscosities of approximately 75,000 centipoises or more. More specifically, as slurry travels through the pump, the slurry hardens due to exposure to air and accumulates inside a cylinder of the pump which thereby prevents proper piston motion in the cylinder and results in malfunctioning of the pump. Depending on the level of viscosity, the pump may need to be cleaned every one to two hours resulting in an inefficient, time consuming and undesirably costly assembly operation.